The invention relates to a coating machine for upgrading sheet material by applying a flowable substance thereon.
DE 36 19 485 A1 discloses a coating machine which permits the recessed or full-surface coating of webs or sheets with lacquer. This coating mechanism essentially consists of a counter-roller functioning as a counter-pressure cylinder, an inking roller standing in contact with the counter-pressure cylinder and functioning as a form cylinder, as well as a coating roller associated with the form cylinder which functions as an inking roller, and an associated dosing roller.
The coating roller and dosing roller in this machine form a dosing system (two-roller mechanism) with a roller gap in common. The entry of the flowable substance, in this case a lacquer, occurs by means of a feed device feeding lacquer into this roller gap. In the printing gap formed from the counter-pressure cylinder and the form cylinder there occurs the full-surface or the recessed coating of the print material by the lacquer.
A disadvantage with the above arrangement is that the flowable substance is applicable to the print material only on one side, and that in the recessed coating a distribution roller must additionally be allocated to the application roller.
It is an object of the present invention to provide an improved coating machine which avoids the foregoing disadvantages and which has particularly usage in sheet-fed rotary printing presses.
Another object is to provide a coating machine that can be operated in line for one-side (front side) or two-sides (front and back side) coating of sheet material. Moreover, during such in line operation, a multiple coating may be applied on one side or both sides of the sheet material.
A further object is to provide a coating machine that is adapted to improve the quality of printed sheet material, or even unprinted sheet material such as, for example, recycling material.
Yet another object is to provide a modular constructed coating machine that can be assembled in series. In this regard, simple assembly is achievable by a coating machine that has, in the conveyance direction of sheet material, a feeder unit, at least one first coating unit for the front side of the sheet material, a turning unit for the sheet material, at least one first coating unit for the reverse side of the sheet material, and a delivery unit. As a further aspect of the invention, second and third coating units for the front side as well as, for example second and third coating units for the reverse side of the sheet material are possible. All the coating units, furthermore, may have the same construction. Only the printing forms and the dosing system need be provided in correspondence to the coating requirement.
Between the coating units for the front side and also for the reverse side of the sheet material, there is arranged in each case at least one transfer drum for the sheet transport, the sheet-turning unit also taking over the function of the transfer drum.
As a further feature of the invention, the sheet turning unit of a series constructed coating machine can be switched over in its manner of operation. Accordingly, the coating machine with its coating units is usable for the one-side as well as two-side coating of the sheet material.
As a further feature of the invention at least one coating unit for the front side of the sheet material and at least one coating unit for the reverse side of the sheet material, in each case having a counter-pressure cylinder and a form cylinder, further having exchangeable coating metering or dosing systems for the processing of the flowable substances. Preferably, all the coating units have exchangeable dosing systems. In that case, the metering or dosing systems are usable in several-coating units with different and/or the same construction.
More particularly, each metering or dosing system preferably has an application roller standing in contact with the form cylinder. The application roller in the particular dosing system is, at will:
a dosing roller assigned to the formation of a common roller gap, in which the flowable substance is feedable into this roller gap, or
a wiper arranged with a circulation system having a feed line and lead-off line for the flowable substance, and in which the application roller is screen-gridded, or
a scoop roller arranged in a supply container.
The form cylinder can optionally carry a flexible planographic printing form, for example a rubber blanket, or a flexible raised printing plate, for example a flexo print plate. Also UV-resistant flexo-print plates are usable.